He doesn't want to sleep in his crib

He has you arapped around his finger. I had my kids in the room with me until they were 3 months old. I had them nap in their room during the day though. I never put my kids to bed asleep. I always laid them down sleepy, but awake. When mine woke up at night and it wasnt because they were hungry or needed anything I went in and patted their back, let them know it was okay and gave them their pacifier. I didnt pick them up or turn on any lights. Soon they were sleeping through the night. Many parents do co-sleep and thats fine for them. If your fine with co-sleeping than you can keep doing with what your doing. There is no wrong to it. Only you need to be careful he dosent smother in your blankets or pillow or you accidentaly smother him. He has learned though if he crys you pick him up and you bring him to bed. They learn quick. Dont let him fool you. You do what you feel is right.

Children are smart little creatures. They soon learn how to outwit their parents. In your case this is exactly what has happened. Your sister is right. Let him cry, and he will soon learn that he must sleep in his own bed. If you cannot teach him by allowing him to cry, get used to him teaching you! You cannot have it both ways!