The I1 individual has A blood type and he is affected. The II1 female is affected and she has AB blood type. Thus, she got A' allele from her father (this A' allele has the nail-patella disease gene) and B allele from her mother. The III1, III5 and III8 individuals also have A blood type and must got the A' allele from their mother (II1).
Thus, it is possible to explain this pattern without a cross over because all the individual who has A' allele (either with blood type A or AB) are affected. As the nail-patella disease gene is present in the A allele, these individuals also got the disease.
In the individual III4, the cross-over is occured because this individual does not have blood type A or AB, rather he has B blood type and got B allele.
The crossing over event must be occurred in the individual II1 between A' and B alleles.