So far as I know, the eldest brother has no romantic entanglements that might cause him embarrassment at his level. Sensibly so.

Knowing this one's ambitions, it was to his advantage to disengage himself from his inamorata. (Not that she herself was objectionable - though perhaps more suitable for a mistress than a wife, if one's taste led one to such things. But the family were, if possible, less socially acceptable than Weasley's own. Cannot imagine the lad speaking as seriously about their futures as he did while never having met her parents, for example. Entirely inappropriate.)

To say nothing of the fact that their somewhat unstable ... relationship ... required him to spend far too much time and energy devoting himself to its repair and maintenance, rather than to the demands of the realm.

Ah. I've spotted him.