They first met just after Llewellyn chose his new life, while he was still working out and finding confidence in showing his mutated arm. It is meeting the other that caused it to realise that there was nothing to be ashamed of.

From there the two then began to grow far closer, and eventually it became almost a parental psuedo older brother figure to the young man. [A lot of the further lore falls into the comfort au stuff I don't feel comfortable sharing online, because people are judgmental over fan ocs sometimes]
However, it does work out who Llewellyn's other father is first, but lets them work it out between them, it's not his place to come in and do anythign as long as no one's getting hurt.