I'm very sorry for your loss. So far since we have owned our house we have never seen or have a witness to foxes being around. That said we have coyotes, coons and possums. I hope you trap and eliminate (or what ever you choose) to protect your surviving babies! Best of luck.
We never see our most successful predators. That's where their success -- their ability to breed and hunt -- lies!
One night I was up very late and heard a noise at my trashcans. I went to the door and saw a raccoon that was stretched up to about 4 1/2' to reach the top of the can. I waved a broom at it and it looked back at me in total contempt.
The next day I called Los Angeles Animal Control and the AC officer told me raccoons were a major presence all over the city and they couldn't respond by trapping such an overwhelming and omnipresent population fed by our trash and our fruit trees. He said I was probably on the raccoon's regular route and I had never seen it because it was nocturnal and I wasn't.
Same with coyotes. Only the very bold and very desperate ones appear during the day but we're more aware of them because of the blood-curdling cries they issue when they're announcing their territory to others. And I learned what the expression "blood-curdling" really means the first time I heard a coyote in my immediate area!
PS The Animal Control folks tell us that killing and trapping coyotes only upsets their natural order and makes the territory we temporarily open up subject to more intense breeding and encroachment from new packs. Our best defense, as humans, lies in a stable coyote population and good deterents like fences topped with rollers -- lengths of pipe strung between uprights -- that trip them up when they try to leap over the fences.