It seems in this contiuity to mean much the same as it does for the human sense.
"Eggs" of sorts with hatchlings appeared in Revenge of the Fallen, as well as in the IDW comics of bayverse continuity. Some of the hatchlings also briefly appear born, at a Decpeticon base in DOTM, where Megatron feeds them. We also had tiny baby dinobots suddenly appear in Last Knight (described as in the transformers wiki: "born at some point following Lockdown's death") - and in the same movie, Hound makes a comment about a bad relationship with his father. Jetfire in ROTF also made a reference to parents.
There's also, as you say in your question, the references to Optimus being a descendant of the Primes: and in Revenge of the Fallen 3 (one of the tie-in comics) he's said to have been orphaned and hidden before Sentinel found him.
So, along with the Allspark method of reproduction - there is evidence to support Cybertronians possessing the capacity of independently reproducing, although that appears to require a significant amount of energy. Hatchlings being described to be dying during ROTF due to a lack of energon.
But as far as a how - we don't know how they do this.
There's actually no information on precisely how they procreate by themselves, only evidence of the aftermath. The only specifics available on reproductive methods being the displayed Allspark one.
Which can bring life to inanimate metal devices, converting them to Cybertronian beings. Although the comics also displayed it being able to create Cybertronians, from minerals on Cybertron's surface: