Aside from what blood will do his family really did not like Poor Dick very much! He seems to have been poor in everything—intelligence, sensitivity, gratitude and familial ties and luck. The Musgroves are rather self-absorbed so perhaps it is also an out of sight, out of mind sort of thing. They like Anne a great deal and as far as I know she has not ever been the least troublesome yet they barely remember to acknowledge the great events at Kellynch:

…she [Anne] believed she must now submit to feel that another lesson, in the art of knowing our own nothingness beyond our own circle, was become necessary for her; for certainly, coming as she did, with a heart full of the subject which had been completely occupying both houses in Kellynch for many weeks, she had expected rather more curiosity and sympathy than she found in the separate, but very similar remark of Mr. and Mrs. Musgrove…

The Mr. Musgroves had their own game to guard, and to destroy; their own horses, dogs, and newspapers to engage them; and the females were fully occupied in all the other common subjects of housekeeping, neighbours, dress, dancing, and music. She acknowledged it to be very fitting, that every little social commonwealth should dictate its own matters of discourse; and hoped, ere long, to become a not unworthy member of the one she was now transplanted into. (6)