As a father of two young children and with couples of friends who also have two children, I can suggest that the idea of designing a babytaraz brother is excellent. The positives are many, they keep each other company, they will exchange opinions and maybe they will need two bathrooms if it's a boy ... but the second bathroom you can take it easy, the promiscuity among children is well accepted until the age of puberty . LOL
Best wishes
The problem is that the first one didn't come easily and if we were to try, it would probably kill my wife. There is a reason we didn't continue :)
In this case it is better to leave it alone