Yes definitely good excuse. If yr family gave to u as a wedding present, of course u should keep, for sentimental reasons.
BUT if yr 99/62 gave u the gold & they want to keep, then I think is reasonable for them to keep. Or if they paid for a lavish banquet or downpayment for yr house, and now want to keep yr jewelry, then I can't say they're greedy. If they "earned" the jewelry, then I would find it difficult to ask. Am I "low toe"?