I'm sorry to hear this. Have you thought about getting grief/bereavement counselling at all, this absolutely isn't just for the immediate aftermath of a loss, a lot of people find their grief really kicks in and they need to process things much further down the line?
Complex bereavement (where you lose a loved one where you had a troubled, complicated or distant relationship) really can be very very difficult to cope with, on a simplistic level you'd think losing someone you didn't always like very much or who wasn't a big part of your day to day life would be 'easier' than with someone who you unconditionally adored and who was with you every day, but that's not at all the case. In the former you are not only muddling up all sorts of other emotions with your sadness at the loss, including shame/guilt/regret about the reasons the relationship was complex, maybe a dose of relief that they can no longer hurt you or cause disruption in your life, anger that you can't address with the person etc, you're also grieving in a way for the relationship you never had and the loss of the potential idealised future you could still hope for while they were alive. The end of the person's live is also the end of your hope that somehow, someday however unlikely, you might manage to repair the relationship or that somehow they'll magically become the parent/partner/whoever that you always ought to have had and deserved. I think it would make a lot of sense if you needed someone, maybe a professional to help you untangle all this and how these ongoing feelings are impacting on your life now.
I totally get the thing about the house and the mementos too TBW, particularly as your brother was involved and you would have hoped at the time of loss that he would be someone you could lean on for support and understanding. After my own complicated bereavement I got quite fixated on physical possessions, I do think these are particularly precious in these complex situations. Again in a more straight-forward loss the most important thing really is all your happy memories of the person, focusing on those can make letting go of actual stuff easier. Whereas if you don't have many good memories, or the ones you do have are tainted by what's come after, you can want to seize on physical items in a way that doesn't always make sense to people who haven't been through something similar and can't understand why you'd treasure something connected with something very hurtful. In a family home too in your case which must have had a lot of generational history. And it does have a nasty sting in the case of a parent if you don't end up inheriting anything either (this was the case for me, well I 'inherited' a big financial and practical mess actually so net financial loss rather than gain) which is the sort of thing again people who don't 'get it' just don't understand - people think you're just grabby or materialistic. For me it's more you feel not only you've missed out on the loving and supportive relationship a lot of your peers have as a matter of course but also on the financial stability that a lot of people get through inheritance too. Again making comparisons to others isn't really healthy (lots of people end up not inheriting very much for lots of different reasons, care costs or money left to a new spouse or the donkey home or whatever, but acknowledging the suffering of others somehow doesn't make your own feel better!) - all I can suggest is counselling/therapy, time, being kind to yourself and trying to be grateful for what you do have in your life including positive relationships, stability, independence etc. It does get better over time, I promise 
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