Depend which panda your talking about the lesser panda has 36 chromosomes the giant panda has 42. However these panda are not in the same family the lesser panda is in the same family as raccoons and the giant panda is in the bear family. How is this possible you ask well raccoons and bears shared a common ancestor which split to form to different families. Both pandas also had a common ancestor which split to form the lesser and giant panda. Bear have 74 chromosomes so you may ask how are they related to panda well analyzing of the chromosome has shown that bears have short chromosomes and pandas long and the panda chromsomes are very similiar to those of the bear meaning that its chromosomes were formed by chromosomal fusion. Thus the lesser panda and giant panda had common ancestor and jointly evolved panda characteristics like the panda thumb then they split one following the bear path on the evolutionary latter and the other the raccoon path and sepeartly evolved there different characteristic such as size difference.