If you'll notice, none of the Collins men have had good judgment when it comes to women.
Possible spoilers!
Roger marries a supernatural creature who nearly kills his son. Then he marries Cassandra, who wreaks havoc on his life, curses Liz, and walks out on him.
Barnabas bedded and eventually married a supernatural creature who wreaked havoc on his life, turned him into a vampire and was indirectly responsible for the deaths of many members of his family.
Quentin marries a gypsy and leaves her flat, has an affair with his father's wife (and God knows how many others), falls in love with Beth, but not for long, reluctantly gets engaged to Angelique, falls in love with the shallow Amanda Harris, and ends up an immortal man, wandering the world in search of a cure, probably bedding every attractive woman who bats her eyelashes at him.
So I suspect the REAL curse on the Collins family was the mens' poor judgment when it came to women!
Love, Robin