No, however that seems like a rather unlikely hypothetical, and furthermore also a somewhat impossible one. If the suicider is literally the only person capable of caring for this person, then there is no one to argue that their suicide would be selfish.
And even then I think it is a tricky issue. I do believe people are entitled to a certain degree of selfish behavior. We are allowed to look out for ourselves. If a person's life is genuinely so utterly miserable that suicide is an otherwise justifiable option, I have to wonder if their right to self-interest trumps their obligation to the child/dependent.