Just need advice..

[KirstyPeach91]

My step son. 11 years old was 8 years old when me and his father were granted full custody of him, after his mother was found to be neglecting and physically abusive. She put men, drink, drugs and herself above the needs of her kids. To make things worse she just turned her back once we had him. Went months without so much as a text and he's seen her 4 times since October 2014. He has a stable loving home with me and his dad but now and again he has these spells of behavioural problems and they range from general 'boy stuff' to hiding things, lies and even letting his sister take the blame. He can be cruel and I've been there for 8 years, I can't keep allowing him to use his past as an excuse when he's had me teaching him right from wrong from the day he was brought into my life. He's got so much love and he's kind and caring and funny and an incredible child. We've explored CYPS in the past and alway been told after initial assessment he's coping well and need not continue with referral but it's so hard being the fair but firm one the one who does the discipline but the shoulder to cry. The one who plays games and has fun then has to become tough. I'm frightened I'll fail him like his own mother did because I can't figure out why he'd treat us the way he does yet went to extreme lengths to protect her when she was so cruel and neglectful