Those style of racks are pretty versitile, I would be surprised if they do not fit.
The only problem may be that as you Citroen has a near verticle rear, the bikes may sit further out from the rear than needed, depending on rack design and adjustments. This puts weight further behind the rear wheels affecting handling. I used a Rhode version of these regularly, but when I need to carry 3 or more bikes I use my old 4x4 (Isuzu Bighorn, Opel/Vauxhall Monterey/ GMC Trooper depending where in the world you live) and a towbar mounted rack. Even that car is affected by the weight of 3 bikes hanging off the rear end.
I would hesitate to put too much weight on such a rack, and I would invest in a reputable brand if the bikes are worth a lot, but I have seen racks like these loaded with 4 mountain bikes. Think about what happens if the rack fails - I had a mate who managed a large bike shop, he often had customers buying new bikes after they fell off racks. One customer purchased 4 new bikes after the rack fell off at 100km/h with a logging truck following him.
If you do go ahead with one of these be aware of the common failure modes- the straps on some models often loosen over hours of driving - so long trips pay speacial attention. Also the ones with the rubber clips that hold the bike, do not trust the rubber. Many internet reviews discuss straps breaking and bikes falling on the road. I always use an independent tie down (bungies are fast and effective), maybe I am paranoid. Also many people discuss problems at speeds like 70MPH - think of the wind pressure of a bike movign sideways at 70mph, even on the back of a car its significant (My car uses 2litre/100km more petrol carrying bikes, all of that is drag caused by the bike....).