Seeing as secrets on soaps *always* come out, it's not going to surprise anyone that Social Services finds out that Steve and Becky paid Kylie to get Max. They then take the lad into their care, leaving Becky devastated. The Star says that David decides Max should be with his mother, Kylie and though it doesn't say specifically that he's the man behind the word in the Social's ear, it's a pretty good bet.
David doesn't really think these things through, though, does he? I wonder if Kylie would get into trouble as well as Steve and Becky. If that's the case, it would be make more sense if Gail grassed them hoping it would rid her of her turbulent daughter-in-law.