I love to think that in a way Bulkhead could possibly have a point that maybe Breakdown is not the biological father, but that the two just don't care. They are happy with their child and don't need any proof to know that they are his dads.
i think they also didn't really plan for it/or thought about it that much beyond "we're gonna love our child with everything we've got".
at this point they're both penniless.
Knockout is trying to scrape up enough money with his escort jobs in order to keep studying medicine (as much as you can study medicine while megatron and optimus are basically having a cold war)
and Breakdown separated from the wreckers to be with Knock Out and does odd jobs as the muscle in several crime schemes that Knock Out either orchestrates or that they get into via Knock Out's escort connections X'D
which is also why Bulkhead and Wheeljack are pissed: in their eyes KO literally seduced their friend Breakdown to the dark side and now he's doing petty theft left and right :'D