Marina asked Van: "But girls - do you like girls, Van, do you have any girls? You are not a pederast, like your poor uncle, are you? We have had some dreadful perverts in our ancestry but - Why do you laugh?" (p. 246 | McGraw-Hill 1969)
Boyd shared in the Ada online annotations: “[Uncle] Dan’s sexual urges, although rarely satisfyingly fulfilled, extend in numerous directions: toward his daughter Lucette, for instance [...]”
I totally missed the part in Ada where Dan's sexual urges extended in Lucette's direction? And I can't seem to find it in the text!
Uncle Dan vs. Uncle Ivan in Ada
Lucette to Van: 'I don't care for your cabochon. I mean it's all right on your dear hairy hand, but Papa wore one like that on his hateful pink paw. He belonged to the silent-explorer type. Once he took me to a girls' hockey match and I had to warn him I'd yell for help if he didn't call off the search.'
'Das auch noch,' sighed Van, and pocketed the heavy dark-sapphire ring. He would have put it into the ashtray had it not been Marina's last present. (3.3)
It seems that Marina has in mind her brother Ivan (a famous violinist who died of lung cancer at the age of twenty), not her husband Dan. Dyadya Vanya ("Uncle Vanya," 1898) is a play by Chekhov. At the end of the chapter Van identifies himself with Tuzenbakh (a character in Chekhov's play "The Three Sisters," 1901):
Worries of her own? Of her mother’s automatic making? A casual banality? ‘We all have our troubles’?
‘Ada!’ he cried.
She looked back, before unlocking her (always locked) door. ‘What’!’
‘Tuzenbakh, not knowing what to say: "I have not had coffee today. Tell them to make me some." Quickly walks away.’
‘Very funny!’ said Ada, and locked herself up in her room. (1.37)
VN's Uncle Ruka (the brother of VN's mother Elena Ivanovna) wrote music himself, of the sweet, rippling sort, and French verse.