cat toileting outside litter tray

Recentlly I had to re-home my male cat due to moving. I found a home for
him, but the owner said that he would hide away and only come out at night
to eat. Wasn't very affectionate, which is unusual for him . Would growl if
any one went near him and he had a very bad habit of toileting everywhere
else apart from his litter tray. She only had him a few weeks and other
people I spoke to about this said that she'd not given him time to settle
into a new home, but she decided to rehome him again. I found another home
for him, a friend of mine took him in. We thought he'd like it there better
as my friend has another cat too, a female and it would be compay.
Unfortunately up until only a few days ago he's been very good on the
toileting side, but my friends now finding toilet mess not only in the
litter tray but around the home, particularly in the kids bedrooms. He's
treated really well and the family love him. We are all bewildered by this.
Has any one got any idea's on this one. Thanks.