Final answer:
The question likely refers to characters in literature, but the provided reference does not give enough context to confirm the exact relationship. Normally, Mortimer, Abby, and Martha are from 'Arsenic and Old Lace', where Abby and Martha are Mortimer's aunts.
Step-by-step explanation:
The question seems to be inquiring about the relationship between Mortimer, Abby, and Martha from a work of literature, but based on the provided reference it is unclear which text the characters are from.
Typically, Mortimer is a character famously known from Joseph Kesselring's play Arsenic and Old Lace, where Abby and Martha are his aunts. However, this connection can't be confirmed with certainty without additional context from the question.
In Kesselring's play, Mortimer is the nephew of the two elderly Brewster sisters, Abby and Martha, who are known for their charitable acts of murdering lonely old men.