Haruka first meets Usagi in the Crown Arcade, challenging her to a friendly match at a racing game. Naturally, Usagi and the other girls are completely blown away by Haruka's skill and good looks. Usagi takes a fast liking to Haruka and Haruka views her as a cute girl, full of energy. Usagi's first encounter with Michiru isn't quite as pleasant; she sees Michiru outside the arcade, talking to Mamoru and instantly becomes jealous. As soldiers, Sailor Moon never seems to give up on Uranus and Neptune. While everyone else initially believes the two outsiders to be untrustworthy, Sailor Moon refuses to believe that they could be the enemy.
Haruka and Usagi's relationship starts out as a complicated one. As Sailor Uranus, Haruka kisses Sailor Moon, taking her by complete shock. Usagi finds herself dreaming about this kiss and thinking about it often… so much so that she begins to imagine Haruka kissing her instead. This leads to a lot of confused feelings for Usagi. If she's thinking so much about Haruka kissing her, does it mean that she no longer loves Mamoru? She can't even look him in the eye due to the guilty feelings she harbours. Personally, I believe Usagi only starts daydreaming about Haruka kissing her because she has such a strong intuition that she and Sailor Uranus are one and the same.
Haruka stops any further romantic advances towards Usagi after Mamoru catches her trying to give Usagi a second kiss. I believe that she likely feels guilty at this point, for causing trouble with Usagi's relationship. Personally, I believe that Haruka's advances toward Usagi are her way of trying to convey the love she has for her princess. While Haruka had no idea that Usagi was in fact Princess Serenity, I believe that there was a force drawing her to that conclusion and the attraction she feels for Usagi was really her incredibly strong desire to protect her princess. I'd daresay that out of all the sailor soldiers, Uranus has the strongest desire to save Usagi from harm, as there have been a few instances where she's been outright distraught at failing in doing so. She also misses Usagi deeply when she's away with the other outer senshi.
As for Michiru, she loves Usagi as well and appears to be completely understanding toward Haruka's protective nature. This, to me, is evidence of the strength of her relationship with Haruka; she never seems to feel truly jealous or envious of the feelings Haruka has toward Usagi.
As aforementioned, Usagi starts out being fairly jealous toward Michiru when she sees her talking to Mamoru. This jealousy is strengthened the more Usagi sees them talking together. There's no doubt that Michiru's extraordinary beauty and elegance makes Usagi worry, but these feelings Usagi has towards Michiru disappear entirely by the time she really gets to know her better.
Chibi-Usa first meets Haruka and Michiru when she's leaving the Tomoe mansion; they're in a helicopter and ask if she'd like a ride home. Chibi-Usa naturally accepts (who'd turn that down??) and they talk about amulets and talismans. Michiru reveals that the mirror she carries with her is a talisman rather than an amulet. This important fact leads Chibi-Moon to realise that Michiru is actually Sailor Neptune and possesses one of the talismans, when Neptune holds up her mirror.
Like her mother, Chibi-Usa feels right from the beginning that Haruka and Michiru are good people. They both act kindly towards her and deliver her safely to the Tsukino residence. Chibi-Moon is absolutely shocked to see that Haruka and Michiru are sailor soldiers and even though Uranus attacks the group, Chibi-Usa believes that both Uranus and Neptune would never actually fight them.
Both Haruka and Michiru love Chibi-Usa and have a strong desire to protect her. Michiru especially harbours a strong sense of love towards Chibi-Usa. Her belief and love for the younger girl is made clear when she gives her mirror to her for safe keeping as a promise that they will someday return. In turn, Chibi-Usa carries the mirror with her and hopes for Michiru, Haruka, Setsuna and Hotaru's return. When the outer soldiers do finally return, Chibi-Usa spends more time with them than the other inners, telling the older women about her adventures, her home, and how she misses her mother. They seem quite happy to spend time with Chibi-Usa and encourage her to do what's best.