my eldest cat passed away, the remaining two are bored and fighting

I used to have 3 cats for many years, until a month ago when I had so say goodbye to my 13.5 years old cat.

The remaining two are a 9yo shy and gentle female, and a 6yo male who asserted himself early on as the ruler of them all.

Now that my eldest is gone, the male looks more "lost" than before: he isn't interested in the toys I give him, he continues to attack the female cat, and looks positively bored.

I thought about getting a 3rd cat, but I feel two are actually enough, as I'm at work for many hours and changing the cat status will only make things worst.

So - how can I make him less bored? what else can I do? 

Are you sure it is boredom, or are they trying to re-establish the hierarchy?  Was your oldest cat the head honcho?

So sorry for your loss!

My eldest was a strong figure in the group and took no crap from the dominant male. However, he did manage to kick her off so he could take her place, but overall she was pretty annoyed by him and wasn't afraid to show it.. 

Now that she is "out of the picture", he keeps bothering the other female, who is very quiet and reserved. He prefers playing with things he's not allowed to, like my cellphone or the TV remote, and has lost all interest in his own many toys scattered around the apartment. 

Perhaps this is just a phase? 

Have you had the boy since he was a kitten and she was already an established member of the household?  Or were all of the cats adults when they came to live together?

I think it may just be a readjustment phase.  It is possible he is bored because he spent a lot of time annoying the eldest, and now the other female has become his target of attention, and she isn't responding the same as the eldest did.  It may be a confusing time for him.  Whether or not they were on friendly terms, he lost a partner/roommate, and this may be his way of grieving the loss of his companion--although they weren't chums.

  It affects everyone on some level when there is a loss.  It's sad to see how the other animals in the household react, and there is always a reaction, even if we don't see it as grief or mourning.  My elderly dog passed away and left my cat, who had spent his entire life to that point with the older dog, was just lost.  His behaviors were very odd for quite some time, and he seemed lost and distracted.  I would find him going room to room howling.  And he knew what happened to his doggie friend, he was there when he passed, and actually sniffed him all over and checked him out thoroughly before I carried him out.  But it tore my heart out to think he was looking for him.  It took about three months before his behavior returned to more of his normal state, and he really hasn't been the same since--and it's been almost 3 years.

There are threads on here discussing the rearrangement of cat "roles" after one passes in a multiple-cat household.  Those may be of help if you search for them as well.  Good vibes to all of you!