Tom Beecher was studying to be a military historian, he did great, extensive amounts of research on WW1 and WW2, and was at the war graves in Belgium when he came across a student, probably the same age as him. He was in love with her intelligence, as well as her otherworldly beauty. She was, of course, Athena. So, they got together for a while, travelling Europe, visiting historic and culturally rich cities, until one day, Athena somehow gave birth to twins, she wasn't pregnant so of course Tom was confused, and his intelligence insulted, he demanded to know answers. Athena, being in love with Tom, told him as much as he could understand, as we was a modern historian, not someone with a great deal of knowledge about Greek mythology. But of course Athena had to leave Tom, heartbroken and with two children.
Tom brought up the twins on his own, never revealing anything about their demigod secret.
The tight family moved a lot, for two reasons, the first being Tom's research caused him to have to constantly move around. The second reason? That was complicated. Alex was a 'typical' demigod, she had ADHD, Dyslexia and mad hyper activity. She often got kicked out of school's much to the disgust of Quinn, who was smart and hard working and hated having to follow Alex around.
Alex was always the popular one, the rebel, the center of attention and Quinn was that nerd who know one really knew. Quinn was bullied, badly, he often came home with scrapes, bruises and sometimes even burns - kids were mean. Some of the bullies were Alex's friends, something Quinn was always angry at her about, but how could she know?
Then one time, Quinn was being pummeled by a beefy footballer, the same grade but twice as heavy and muscular as poor Quinn and something weird happened. Somehow, Quinn knew what moves the bully was going to make, like a sixth sense. After 5 minuets the bully was crying on the floor.
Despite his new 'power' Quinn's life did not become easier, he was a freak now, an even bigger target for more ruthless bullies. He took refuge in comics like the X men, knowing that he was not alone.
On the other hand, Alex was experiencing weird occurrences of her own, she knew she was always smart but never used it, fearing it would damage her reputation as a bad girl. But she could never weave, she hadn't even though about weaving - how weird was that? Weaving? Then suddenly wall's of random objects woven with accuracy appearing around her. Unlike Quinn, her 'power' was a very much a secret. She began to dive deeper into the 'bad crowd', getting involved with alcohol and petty crime.
Tom was not happy, he was a well established historian and worked hard to give his kids as much as he could, and suddenly one of kids never left his bedroom and the other never returned home. He was tolerating Alex's behavior until he had to bail her out of a police cell after she was caught drunk driving home from a reckless party - she was 12!
They took a 'vacation' to Canada where Alex could 'detox' and Quinn could get some time where he didn't constantly feel threatened. That luxury didn't last long, while the twins were finally enjoying themselves together, canoeing on a secluded lake, they were attacking by three telekhines!
Having very little battle experience other than their father's long talks about the trenches, the twins abilities were put to the test, Alex recklessly tried to lunge at one of the monsters, but her instinct pulled her back (and her brother). It was clear to Quinn they needed weapons, and to buy himself and his sister some time, he built a weaved wall from nearby reeds. Both twins racked their brains for anything, but they needed weapons and they didn't have swords and daggers just lying around.
This was when Tom came to the rescue, after a desperate phone call from Alex he came rushing to the lake with a (celestial bronze) sword he had been given by Athena years before, the twins worked together with their new found battle skills and strength, distracting the monsters and launching surprise attacks. After a long and strenous battle all their foes had evaporated into gold dust, the twins were left battered and exhausted. Tom saw the battle as he had the sight.
After that Tom told the twins all he knew about their mythological past, they had to believe him, because it was only the reason to explain their powers and the monsters. Along with the sword, Athena had written Tom the address to Camp Half Blood, so he drove the Twins their as a place of safety for them.
When they arrived at the camp border, another swarm of telekhnines emerged from the surrounding water, there were too many to defeat with one sword but luckily, they had a camp full of demigods on their side, and the monsters were defeated in almost seconds. The demigods were welcomed into camp and Tom went back to his career as a historian. The twins still find ways to visit and spend time with their dad.