Someone who's companionable is close and friendly. A companionable dog stays right by your side, a loyal pal.
It's fun to talk to a companionable person — they tend to be warm and good-natured. And our best relationships are the ones that are the most companionable: your grandparents might say the secret of a long, happy marriage is to make it a companionable one. A companionable silence is comfortable and relaxed. The word stems from the Old French compagnon, "fellow, mate, friend, or partner."