Quentin is 27-28 in 1897. We're stuck with that 'cause his year of birth is given as 1870. That's fine though, because Selby was 27 when he started on the show and turned 28 soon after.
Even though Edward is referred to as the eldest, he is often referred to as the eldest
son. Back then women weren't given as much consideration when it came to family pecking order, so to speak.
I consider Judith to be the eldest child, followed by Edward. I put her at around 45, and Edward at around 42-43. (It's somewhat conceivable - people didn't age as well back then).
That leaves Carl. I'm sure many would disagree, but I think he's older than Quentin. Quentin is the youngest. I feel he was spoiled by his mother, and he was her favorite. Judith and Edward began resenting him from the moment he was born.
I think Carl is a couple of years older than Quentin -- around 30-31. It's usually assumed he's younger, but that's because of his childish ways, silly antics, and a lack of intelligence in certain areas. I think he wasn't quite normal when he was born, and had some delays.
So...there ya go. (For what it's worth) LOL
-CLC