My wife looks over my shoulder from time to time when I am painting or on the computer. One time I was looking through a folder on my computer where I save my work, looking at the thumbnails my wife jokingly remarked,"I guess I'm your muse".
There were at least 15-20 images of paintings I've done of her.
The next easiest model other than my self has been my wife. She is almost always ready and willing to sit for a painting or strike a pose. Unlike our kids I don't always need to rely on a photograph because she has the patience to sit still and I never get tired of painting her.
It helps to have someone who is supportive, (even though she’s not crazy about my dinosaur stuff), and understands that this, (art), is something I do because it’s a part of me I can’t ignore.