My husband’s first wife died so conflicting parenting styles were never a problem with our family. However, my stepson was quite a manipulator so my husband and I very quickly agreed that any money going to him would go through my husband. All I would ever do is smile and say “Let me talk to your dad about that.” If he stomped off indignantly then I knew he had already asked and either been turned down or had gotten what he wanted but had spent it on something else (he was and is a bit impulsive).
My brother’s family is the ultimate in blended families. This is the third marriage for both. My brother has three kids from wife number two, who is doing her best to completely discredit my brother and drive the kids absolutely nuts (she now also has a stepson from her live-in boyfriend). His wife has one child from husband number one (he died and so is out of the picture), one child from husband number three (who is a male version of wife number two), and a stepchild from husband number three who saw through her dad years ago and considers herself part of my brother’s family. They also are raising a granddaughter and giving house room to two boys who have problems at home. Their house also serves as a gathering place for random teenagers, boyfriends and girl friends, and college kids who need temporary parent figures.
In general everyone gets along well with two exceptions. One of my brother’s daughters hates to have the limelight on anyone else and so has caused assorted problems with almost everyone over the years, including all the kids and all the adults at all the houses. And his wife’s oldest son has a bit of a problem with impulsiveness (hence the grandchild) leading to a variety of “interesting” legal adventures and job changes.
The main reason I think is that both my brother and his wife generally accept and love all children indiscriminately, no matter their flaws or foibles, as long as they make at least some effort to keep the house from exploding due to a build up of noxious laundry and fermenting dishes, and as long as they do their school work. In addition, all discipline is performed jointly with both adults present, so no one can be accused of being unfair.