We have gone through a number of luggage sets in our life times. The adage, they don't make then like they used to definitely applies. Also, newer luggage is often lighter and more innovative in terms of space and capacity. Currently, we have a set of Briggs & Riley that is holding up pretty well despite inept baggage handlers who completely destroyed one piece the first time we used it (B&R replaced it without hassle btw).
Anyway, when we pack for trip, we cross-pack. That way if a piece of luggage gets lost or way-laid, neither of us is completely without clothes to get by. While a "no sharing" policy sounds like a good idea between strangers, it spells potential disaster for the unfortunate family member whose luggage was lost/delayed in transit.
On our last voyage, we met a woman who had her luggage left at the hotel (her package included pre-voyage tour, transfer to the ship, etc). She went the entire 15 days without her own belongings or clothes because someone failed to pick up her bag and place it into the shuttle between hotel and ship.
The primary question is - Do you really want to take that risk? It's your choice but where family/close friends are concerned, it makes a lot more sense to cross-pack.