Why does my 60 pound dog try to sit on me when I babysit my baby granddaughter?

Could be jealous, trying to keep/get your attention. Could also be protecting you. No one goes near his momma! My dog does this sometimes when my husband tries holding my hand. What I do during these situations is, continue to hold my husbands hand and also pet my dog with my other hand. This way he knows I am ok and that I am still able to give him attention as well. :)

Sounds like jealousy or territorial (ownership I think more than protection it sounds like). My dog Miko does that when his friend Django stayed the night and when our puppy friend Loki wants attention. He'll position himself on me closer than Django or between my legs when Loki is in front of me and just lean on me. I'll pet Miko and pet or play with the other dog which makes Miko know he's still loved and it's ok for me to play/pet/snuggle with other pups as well. Miko is 130lbs if that makes you feel any better :-)

Sounds like your pup is a little bit jealous! My dogs always come close to me when I'm petting other dogs, most likely as a way to gain my attention and tell the other dog that I'm their owner. It shouldn't be an issue unless your dog becomes aggressive or territorial. It's most likely just a way for him to show his love and affection for you!