Getting belgian visa after having baby with belgian citizen

It will simply suffice to make an acknowledgment of paternity. From there, a six-month orange card will be given to you and after six months you will receive a cartfee F. This card will give you a right of residence of five years and the same rights as a Belgian citizen.

Do i apply for family reunion visa first or come on tourist visa

For family business, immigration's office hate peoples who start process with tourist visa.

Ok  then I go for family reunion

If you have fiancé here in Belgium tourist visa has nothing to do with it. Apply for family reunification or fiancé visa if you guys wanted to get married here in Belgium (like what we did). Tourist visa is only for those who doesn't have family or fiancé here in Belgium because their main goal is to tour. If it happens that someone applied for tourist visa and the sponsor is his/her fiancé there is a big possibility that the visa application will be denied. They're thinking that this specific person who are applying for tourist visa will not come back  to his/her homeland, which happens alot that is why they changed the rules and get more strict every now and then.