Questions on church records

Hello Everyone! I have a couple of questions. First, is it possible for babies not to be baptised? I'm looking everywhere for my 4x & 5x grandfathers, with approxmiate dates of 1787 and 1807. Up to that point, all births in my family are in the Aquascalientes area. I've searched all the records in Aquas., and I'm well into the Zacateca records. Their names are found on marriage records but that's all I've been able to find. Secondly, when the church records "no conocidos" are written, I am assuming the baby is illegitimate and godparents will raise the child, or is he/she given to an orphanage? Thanks in advance. I've learned a lot from this website. Carol