Sparky10, i think that the others have made some excellent suggestions.

My much-loved cat Susie, who died last year as a 23 y.o., howled a lot after her companion cat Spike, as a 22 y.o., died the previous year. I suspect that she missed him.

One thing that you could think about is getting a replacement cat or dog to keep Tigger company.

This may not work because Tigger, as a 17 y.o., may find it hard to deal with a new companion animal but it might be worth considering.