Papillons Hard To Housebreak?

My Papillon is a year and a half old and he wears diapers! I tried until he was almost a year old to house train him and he knows to go outside and will sometimes, but as soon as we get back inside he thinks it’s ok inside too. He lifts his leg and pees every hour or two while inside, no matter what I do! I heard that Papillons are very, very difficult to housetrain. And pooping-whenever he feels the urge he just poops, wherever he is! Is he going to have to wear diapers his whole life? I also have a 4 yr old Rat Terrier and she likes to pee inside too, on the rug! She knows it’s bad, she knows to go outside. She can hold it a long time, but she’ll be bad and pee on the rug! I don’t know what to do, maybe I should find her a new home?? I can’t have them ruining my things, they are expensive as it is!