Need advice from Step Fathers/Fathers please

The little guys are looking for continuity. No Male in the house puts the burden on the Mother. Kids like men, because they are not mom. If you are serious about sticking around, then let them know it. They will get better.
I raised four kids, and my Daughter married a Man who has parttime custody of his two boys , and the boys have a terrible mother. So they follow grandpa around when they come to visit. The Boys are getting better behaved, as they know the rules at Grandpa's house! Boys like rules, they just want the rules to be consistent. They may complain, but that is what they do.