It does suggest that <PERSON> (and maybe <PERSON>) has a jollier side as most children reflect their parents (<PERSON>'s children are vain and/or caring, <PERSON>'s are arrogant etc). Now in theory <PERSON>'s cheeriness could come from her mother but from what we see of <PERSON> this seems unlikely. Maybe she was cheerier before the curse but I doubt it. Looking at more evidence for a jolly <PERSON> I found a little but not much.
Before I go into that we need to remember a few things. We see very little of <PERSON> in the books. He speaks to <PERSON> in a flashback and I think we see him again later but mostly who we see is <PERSON> talking to <PERSON> or <PERSON>. This is important as the two are different, <PERSON> is less respectable, he is very much a death god. <PERSON> on the other hand is a god of riches and wealth as well as death and is seen as moderately more acceptable. This can be seen in the way <PERSON> is much more accepted by the Romans than <PERSON> by the Greeks. 247
Another big factor is how <PERSON> feels in his appearances. His partner was murdered by <PERSON>, his children forced into hiding and he is shunned by the Gods. This is on top of all the bad stuff that happened to him in the myths and his appearances in <PERSON> are always when he feels he has been wronged or is in a stressful situation.
In the books there isn't much evidence for <PERSON> having a happy side. He tells a joke, maybe two, in Blood of Olympus chapter 14:
<PERSON> allowed himself the slightest smile but there was nothing cruel in his eyes.
This comes straight after him teasing <PERSON> about his obsession with <PERSON>. He also says to <PERSON>:
Prehaps your chambers would look good decorated with the skulls of monks.
And after this his eyes glitter, possibly showing merriment.
He cares for his children and lovers, he gives <PERSON> some presents and begs <PERSON> not to endanger her as well as telling <PERSON> that he should try to be happy.
I believe but can't find the section that <PERSON> also seemed more cheerful when with the <PERSON>' mother.
I believe the reason for <PERSON>'s lack of cheerfulness is summed up here:
You convinced me too let go of my anger
Emphasis mine.
<PERSON>'s anger at his unfair treatment is what keeps him so upset. When with his children he seems to occasionally overcome his anger and be happier. On the other hand when <PERSON> is alone his anger intensifies. <PERSON> is also angry and alone which is why he shares <PERSON>'s personality. <PERSON> is usually not alone, being either with <PERSON>, <PERSON> and <PERSON> or <PERSON>. In Alaska when she was isolated she does become sadder and less cheerful.
I would say <PERSON>/<PERSON> could be cheerful if he was with people but his exile from his family on Olympus and the 6 months he spends without his wife cause him to become sour and angry, squashing his happier side. 247