Just a little concerned

So I'm a mommy of 2 kids. My daughter is 2 years old and my son is a year old but I've noticed my son is a little lazier I would say compared to my daughter. My daughter began mumbling and babbling at 5-7 months and on her 1st year she was actually able to have broken conversations. But my son on the other hand is a year but won't say any other words beside : momma, dada, ma & pop (grandma& grandpa) titi and our family dogs name but he won't pronounce any other small words we try teaching him, he points, cries, whines and sits by the things he'll want and he likes to play alone all the time. He does play with his sister but when they do he ends up hitting her when he wants her toys (since he can't talk and ask) or he'll just take her toys and walk away. He's not social with anyone in the street and sometimes even with family. Should I be concerned that he's learning at a slower pace than my daughter ?