There are two studies I have available. One shares the ABO type, the other the Rh factor.
This one told us they were blood type O:
The high polymorphism rate in the human ABO blood group gene seems to be related to susceptibility to different pathogens. It has been estimated that all genetic variation underlying the human ABO alleles appeared along the human lineage, after the divergence from the chimpanzee lineage. A paleogenetic analysis of the ABO blood group gene in Neandertals allows us to directly test for the presence of the ABO alleles in these extinct humans. We have analysed two male Neandertals that were retrieved under controlled conditions at the El Sidron site in Asturias (Spain) and that appeared to be almost free of modern human DNA contamination. We find a human specific diagnostic deletion for blood group O (O01 haplotype) in both Neandertal individuals. These results suggest that the genetic change responsible for the O blood group in humans predates the human and Neandertal divergence. A potential selective event associated with the emergence of the O allele may have therefore occurred after humans separated from their common ancestor with chimpanzees and before the human-Neandertal population divergence.
https://www.researchgate.net/publication/23698814_Genetic_characterization_of_the_ABO_blood_group_in_Neandertals
But wait… this one is new and… it may blow your mind:
Variation at the ABO locus was one of the earliest sources of data in the study of human population identity and history, and to this day remains widely genotyped due to its importance in blood and tissue transfusions. As one of the first genetic markers, variation at the ABO gene has been studied for over 60 years, and yet there are some aspects of its evolution that remain mysterious. Here, we look at ABO blood type variants in our archaic relatives: Neanderthals and Denisovans. Our goal is to understand the genetic landscape of the ABO gene in archaic humans, and how it relates to modern human ABO variation. We analyze coding variation at the ABO locus from next-generation sequences in ∼2,500 individuals from 28 populations, including three Neanderthal and one Denisovan individuals. We use the modern human haplotypes to impute ABO genotypes for the four archaic human genomes. We found that the Siberian Neanderthals, Altai and Chagyrskaya, are both homozygous for a derived Neanderthal variant of the O allele, while the European Neanderthal, Vindija, is a heterozygote for two derived Neanderthal variants, an O variant different from Altai and Chagyrskaya, and a rare cis-AB variant. The Denisovan individual is homozygous for an ancestral variant of the O allele, similar to variants found widely in modern humans. Perhaps more surprisingly, the derived O allele variant found in the Altai Neanderthal can be found at low frequencies in modern European and Southeast Asian individuals, and the derived O allele variant found in the Vindija Neanderthal is also found at very low frequency in East Asian individuals. Our genetic distance analyses suggests both alleles were introgressed through Neanderthal-human gene flow. In summary, our study identifies the genetic variation of the ABO gene in archaic humans, we find that ABO allele diversity in Neanderthals was likely high, and that some of these alleles still survive in modern humans due to inbreeding with Neanderthals.
https://www.biorxiv.org/content/10.1101/2020.07.27.223628v1.full.pdf
See also:
Human genetic variation in the ABO gene is a classic marker for genetic diversity in humans [Cavalli-Sforza et al., 1964]. Here, we provide an in-depth description of the genetic diversity of the ABO gene in four archaic humans, based on published ancient genomes. We found that archaic ABO haplotypes are polymorphic at the same positions which define modern human ABO function, and have posited that these archaic alleles must function similarly to modern human alleles. Furthermore, we found Denisovan-specific O alleles, which are genetically similar to modern O alleles, while Neanderthal-specific O alleles are derived relative to human alleles, but found today at low frequencies due to past humanNeanderthal admixture. Finding four different Neanderthal variants in late-era Neanderthals is unexpected. A common perception, based on long runs of homozygosity seen across Neanderthal genomes, is that late-era Neanderthals were extremely inbred and thus had reduced genetic diversity. The high allele diversity found in these Neanderthals was possibly maintained through balancing selection at the ABO locus. This notion dovetails with our contour map results, showing introgressed Neanderthal O haplotypes falling outside of the genome divergence of all other fragments, and suggests that balancing selection operated in Neanderthals similarly to modern humans.
The only data on Rh factor shows Rh positive
See also:
At least two of the extinct, ancient humans had type O blood, making them the “universal donor”, according to a new genetic analysis of remains of 45,000 year old individuals.
https://www.newscientist.com/article/dn16386-neanderthals-might-have-made-good-blood-donors/#:~:text=At%20least%20two%20of%20the,of%2045%2C000%20year%20old%20individuals.
When scientists tested whether Neanderthals had the O blood group they found that two Neanderthal specimens from Spain probably had the O blood type, …
https://humanorigins.si.edu/evidence/genetics/ancient-dna-and-neanderthals/dna-genotypes-and-phenotypes
When scientists tested whether Neanderthals had the O blood group they found that two Neanderthal specimens from Spain probably had the O blood type, though there is the possibility that they were OA or OB (Lalueza-Fox et al. 2008).
https://humanorigins.si.edu/evidence/genetics/ancient-dna-and-neanderthals/dna-genotypes-and-phenotypes#:~:text=When%20scientists%20tested%20whether%20Neanderthals,2008).