In my book because an unselfish person would consider what is right for a child not themselves! The definition of selfish I understand involves behaviour that puts the self's needs/wants/rights before other peoples (especially those who have no say in the matter).
And I suppose you have an intimate knowledge of what Elton and David are thinking? If they want a child, and have love to give, why not have one?
In your opinion how will the child be deprived of either love or material things?