Should i have another baby just to keep fiance?

i am 23 years old and my fiance is 32. we have been together for almost 2 years and have a 13 month old son. he has been detached from our son since the day he was born. he only says the word "boo" to him and at first denied he was even the father. we live with my parents in one small bedroom upstairs. our son has a tiny corner of the room that was formerly an upstairs landing. i feel like my fiance only wants to live here to escape his alcoholic mother who he also wants to live with us if we do move out. he is talking about jhaving a baby girl even though we both work seasonally and spend all of our money on video games and movies. he wants to have the baby girl and continue living with my mom and dad paying $175 for everything we use here. i admit that my mom does most of the work in caring for my son. i don't do his laundry or bottles or anything like that. but i would like to have another baby. my mom is opposed to the idea but i think my fiance will go back with his mother. ???