hi,
yeah 8-10 per Leater is kinda normal for a family car I guess (except the VVTI toyotas and maruties). My fb15 does like 8.5-9 and some say that their cars do about 10... so what I think is it all depends on the way you drive and the traffic that you are riding in. it could be 10km per L or it could be 8km per L or may be ever lesser. So, if you are looking for a family car which has good space and you can find spares easily and if it fits into your dream then go for it. That's the best thing to do.
And Hondas... I think they are good cars and much better in performances than the nissans. But the spares... you'll have to spend a lot on spares. That's my concern