how do I convince my parents to have a baby?
Do you realize how it's not that easy to get pregnant in the first place when you actually want a baby?
When you are pregnant, it is very painful and difficult, and then comes the worst pain of them all - childbirth.
Raising a baby is also difficult, and extremely expensive.
It sounds like you don't really understand what you are suggesting.
Lol, this is a new one, rather then trying to have one yourself you want to get your mother pregnant.
+1 for creative thinking.
Unfortunately there is nothing you can do to convince them to have another child. Tell them you think it'll be cool, but in the end it's their choice.
whatever you tell them its up to them, I doubt you are going to be able to convince them to have a baby so you can play with it.