One time, this was almost literal - a small child was used as a missile by a supervillain (Malice, of the Bad Girls) in a Champions game. It's not a very effective thing to do, as they are limited in the damage they can inflict by their low BOD and zero DEF. Paving slabs are more effective.
As for the idea of inflicting parenthood, even adoptive or something like, and transient, it was never explored while I was involved. Heck, we didn't even have any “spunky kid” PCs (thank goodness, worse than kender…) The only episode I can recall in which children actually appeared was an almost off-screen incident in the Glorantha/RQ game where the PCs had returned to their home steading, and my Babeester Gor axe-murderess was co-opted by the Voria nursemaid as an assistant. This being a cult obligation, she grimaced, went along, and into an off-screen interlude.
Subsequently in the same GM's Saxum Caribetum saga, I gather the mages get involved in orgies, sparked off by faerie wine, which have resulted in offspring as well as points of vis, but I get the impression that the grogs are left to deal with the sprogs. There may be more sordid details on the campaign web page than I wot of.