From my distant memory -
Before he married Leila , David was (?) married to Alicia
Jacob was being raised as her son, but his birth mother was Leila ( Alicias sister) who had copped off with her BIL (Alicias husband )
Their Mum persuaded her to have the baby and let Alicia bring him up ( I don't think Alicia could concieve )
No idea if David adopted him but Alicia escaped to Portugal or somewhere and his dad was never on scene , so he was left with David and Leila