Shinobi (Ninja) Squads
The shinobi squad ratios in the television version of Naruto only appeared to have a ratio of 2:1 because the show focused on the adventures of the warriors of the Leaf Village. The ratio of different groups would also end up being very different depending on the village, clan or social group a ninja belonged to. This does not mean other villages did not operate the same way but their rationale might be complete different depending on the number of ninja at their command.
In the Leaf Village, once a ninja initiate became able to take on missions, usually at the rank of Genin, they were assigned to a squad of three with a Jounin-level leader to provide guidance, coordination and experience to the other members of the team. Personalities would occasionally be considered for mission compatibility depending on the nature of the mission or the shinobi. In the event of a team needing backup, a second group of three Genin plus one Jounin would be assigned to support.
ANBU Black Ops traveled in groups of 4 to 8 members depending on their mission. This allowed for strength, reconnaissance and redundancy always ensuring a member of the team could return home with information gathered from their stealth operations.
In such teams, the members were chosen, not for their sexual orientation but for the compatibility of their styles of fighting OR the compatibility of their techniques. This compatibility was looked at while they were still members of the Academy and promoted to ensure teamwork and coordination as they grew in power and skill.
If you were a member of the Akatsuki, one of the show's major villain groups, you would be traveling in teams of two, chosen for jutsu compatibility. Personality was far less likely to be a factor in your relationship with your partner. Your partner would likely have shinobi jutsu techniques that were able to be utilized in a fashion that the two of you were a force to be reckoned with even against other elite shinobi.
Each of the trios we see from the Leaf Village tried to mix, reconnaissance, stealth, fighting prowess and healing ability in all of their groups. The Leaf village was also fortunate in having a relatively high number of elite and specialist ninja they could call upon.
Other villages were not as fortunate, as many of their members where killed when the Great Beasts (Jinchuuriki) roamed the land before they were sealed away or destroyed. Later warfare would take a toll on many village shinobi reducing their numbers further.
The definitive reference for this show and manga is: Leaf Ninja.com