A bit of context could provide some useful hints, such as for instance whether the wife is the child's mother or just someone's wife, or whether the speaker is their father and husband or rather a scientist watching them through a one-way glass. But I suspect that Alex served them us clipped off the page on purpose, as a challenge.
The only clue left is the indefinite article used for the child, which would suggest either that the child is one out of many in the family, or that the sentences come from a scientific or pseudo-scientific publication (but in the latter case also the wife would likely be a wife).
Like this, out of nowhere, the first sentence "Love which is greater for a child than for the wife" can be read in two ways:
1: someone loves a child more than the wife
2: a child appreciates/needs love more than the wife
Whereas the second one, "Love which is greater for a child than the wife", could mean that for a child love is more important than the wife (a child needs love no matter from whom it comes).
Grammatical correctness (someone will differ) can be long debated and negotiated, but helps very little per se if the sentence is ambiguous or doesn't reflect what the speaker is trying to say.
This is as far as I go.