We need family tree of Sonicstep and Bassline! And Headcanons of their family!
Jazz and Blaster are orphans, and grew up (survived) on the streets of Iacon, so they called each other brothers.
Prowl and Springer are actually father and son, Springer was artificially created using Prowl's DNA. Since Springer born very small, Prowl raised him not as a son but as a brother, because according to the strategist, he was psychologically not ready to be a father, so it was easier for him to consider Springer a brother. Everyone who knew the truth (Optimus and Ratchet) promised not to tell anyone. Springer himself does not know the truth.
Tracks had been courting Blaster for quite some time, but he did not reciprocate (Blaster loved Tracks very much), because he was afraid that Tracks would abandon him if he found out that all 5 cassette bots were his children. But the cassette bots themselves wanted their creator to be happy, so they told Thrax the truth, and over time Blaster and Tracks became conjunx.
Blaster and Tracks' baby is named Dashbeat (or Dashy for short)
Blaster was the carrier, after all, quote: "I already had three sparks in the forge, it will be easier for me to carry one big spark!"
Springer and Hot Rod had known each other since the academy, but their relationship took a new level when Springer saved Hot Rod, at that moment the spark both of them was pulsing like crazy. They had been dating for literally three months and Springer immediately proposed to get engaged (which caused a complete shock to Prowl, because it was too fast)
Almost immediately after the ceremony, Springer sparked Hot Rod, and they were born a mechbot called FlameSpark
Dashbeat with twins of the same age, while FlameSpark is the youngest of all the Sparklings
