Venting

Ok my SIL just moved to Texas where I live for 3 days now so far her baby has been at my house 2 of those days the father of the baby hasn't seen his baby in 2 weeks and he saw the baby for 20-30 minutes then sent the baby to my house for 2 days straight! I'm upset that both of his parents don't seem to care about him! When he is over with his parents they hold him for like 5 minutes then sit him in a bouncer in front of the TV and leave the room and don't spend much time with him! Also his mom says that he has all these issues like he never sleeps, always spits up (to the point of needing medication) and he has to sleep on his side so he doesn't choke on his spit up! When he is with my fiancé and I he sleeps all the time, he only spits up spit up like 3 times the entire time he was with us for 2 days! One of those time was after his mom came to drop off more diapers and feed him! She thinks she should only burp him every two ounces since it's easier and I burp him every ounce since he is having so many acid reflex problems! Also her idea of burping him is just patting him on the back like 3 times then feeding him more wether he burped or not then he spits up the entire bottle! And they leave him with me and bitch at me for the way I take care of him when I'm doing better than they are he has no issues when he is with us! So am I right in the way I feel about them not caring or am I just jealous of them having a baby and am trying to find any reason to be mad at them since I don't have a baby and I want one!