Going back to Margaret's arrival in 1948 her mother shown as a Mrs. McClure - just checked SP and a Jeanie McGuffie Milroy married a Walter McClure 1924 Maybole (the year after Margaret's birth).
And now for the object of this thread - Allan Neill - and 'eureka'!!
Margaret Handlin Milroy married said Allan Neill 30/1/1940 Carrington, Midlothian, details as follows:
Allan Neill 22, plumber, of 11 Sanghree (??hard to read) Cottages, Rosewell, son of Allan Neill, coal miner, and Agnes nee Houston
Margaret Handlin Milroy 17, of Edgelaw, Gorebridge, dau. of Jeanie Milroy, afterwards married to Walter McLure, ploughman (fathers details just has a line through it).
Witnesses were a Jessie R G Milroy and Thomas Cooke.
(His parents married in 1917 at Galston (Ayrshire) and as he was 22 in Jan.1940 when he married Margaret he was probably born late that same year - SP shows an Allan Neill birth in 1917 Hamilton (Lanarkshire) which may possibly be him.
Possible birth for a daughter with the Christian name previously mentioned plus initials J.R in 1941 at registration district George Square (Edinburgh).
So, did Allan Neill and Margaret divorce? I can't see any casualty for this name being killed in WW2.
Just checked on SP for a death entry for an Allan Neill bc.1917/8 and there is just one in 2009 Edinburgh Central so possibly him and if the couple did divorce he probably would have remarried too.
Whatever happened, clearly Margaret had care of her firstborn daughter and presumably something happened around/soon after the birth of their 2nd child so without knowing the details don't think we should malign the lady too much. Allan could have deserted her and she simply couldn't cope with a newborn baby and a toddler.
So, at least we now know who Allan Neill was and that he and Margaret had indeed been married.
Annette