A> No motive, they stand to gain 0.
B> Any hand can win!
C> Sounds like you're playing low limits, where people do anything
D> If you're colluding with your brother, prepare to lose your account, and your funds. PokerStars is great that way, if you've involved in a tournament with colluders and PS catches them, even if you were unaware and lost the tourney, you could earn a big profit! They take all the money you had in your account, and distribute it to the players you were playing against. I got $50 once!
E> Bots can only do one of the 3 things that a human can do - call, raise or fold. The only advantage they may have is being smarter than you.
F> The percentages only work out over thousands of hands. Even the best players sometimes can't win a pot or table for long stretches, by playing the same way they always play.
Pokerstars isn't in the business of playing poker, they have everything to lose and absolutely nothing to gain by cheating. Even in a $500,000 hand, they stand to gain $3, which they made before the cards were dealt.
To add to that, I generally throw in $100-200 and play a mix of cash games, sng's, omaha, etc. Most times I run this money up to about a thousand bucks on a steady run, then lose it all. Over and over.
This last time I just cashed out I think $1200 and said fuck it, I'm gonna win this time!