Felix is seven months old. He can sit up (as you can see). He usually doesn't sit up for long, but he is capable of doing it. He can also crawl - sort of. If he really wants something he will stretch and squirm until he gets it. I think by next month he'll be a full-fledged crawler.
Even though he's fairly short and light for his age, (third percentile for weight at his last checkup), he has pretty chubby thighs. Felix wears clothes meant for babies aged 3-6 months. Most of those clothes still have plenty of room. He's also really bald (like his brother). (In general he's looking more and more like his brother as he gets older.)
This past week he went to the sitter's with his older brother, and he seems to have adapted well to that. I sure did miss him while I was at work, though.