PMB was thinking of 'I am a Brisk Young Sailor' (Roud 1042). Quite rare -three versions, I think, in the Gardiner collection, all from Hampshire. I doubt if there is any paedophiliac subtext; 'child' in this context usually just means a girl -or woman- much younger than the person describing her (as in 'child bride', a common Victorian term).

Equally, the often cited examples of 'Our Captain Cried' and 'Willy of Winsbury' are really just commonplace ballad conventions and only appear sexually ambiguous in the light of what (I think) Sharp described as 'modern prurience'; it is pretty unlikely that your average traditional singer had any such thought in mind.

Much thought and many words have been expended on sexual ambiguity in the plays of Shakespeare and his contemporaries, where cross-dressing as a plot device, and the fact that all parts were played by men, provide plenty of opportunity for multiple levels of meaning; but that, really, is another matter; though there is also much useful discussion on the whole 'cross-dressing' business as it applies to popular song in Dianne Dugaw, Warrior Women and Popular Balladry 1650-1850 (Cambridge University Press, 1989).

There were certainly broadside songs that dealt with lesbianism, but there's no evidence, so far as I know, that any of these survived in tradition to become what would later be called 'folk songs'. That doesn't necessarily mean that none did; but it's pretty unlikely that any Edwardian singer who knew one and understood what it was about would have dreamed of singing it to a folk song collector (or any woman).

PMB has explained why male homosexuality doesn't really appear in folk song; I'd add that references to it certainly appeared on broadsides, but these were usually extremely hostile; and topical, apparently not surviving in tradition.

Modern composed songs are irrelevant to the question asked. Rugby and other specifically scatological songs are really the only places where you'll find references that might count as 'traditional', but these are invariably concerned with the physical act only, whether it be 'same sex', zoöphilic, or whatever. Relationships don't enter into it.

For relevant historical material, see in particular

http://www.immortalia.com/