Childhood, for many siblings, is a very competitive time. Sisters and brothers try to out-do each other, which leads to fighting, and eventually, many can’t stand being in a room together. That four siblings would get along with each other enough to commit to spending extra hours each together – nearly all their time – to form a family band and be trapped in busses for months on-end; well, that’s highly unusual.

The Sierota siblings of alt-pop quartet Echosmith, who will perform Sunday at BottleRock Napa Valley, have maintained a band for eight years. That’s a good chunk of a lifetime for 18-year-old Sydney (vocals) and her three brothers, 22-year-old Jamie (guitar), 19-year-old Noah (bass), and 16-year-old Graham (drums).

“When we were younger, there were definitely times where we would fight, as any other sibling would,” Sydney said two months earlier at a San Francisco stop, touring for the second straight year in support of 2013 debut album Talking Dreams. “But we generally got along really well and chose to be friends. I remember hearing my friends say, ‘I hate my brother.’ I was, like, ‘Oh, that sucks. I love my brothers.’”

Close confinement hasn’t created an imposition on the Sierotas, because each has some semblance of a personal life – none more so than Jamie, who is now married. In his spare time he has taken to leatherworking and making bags and photography.

“Noah is a really amazing chef and Graham…is a big soundtrack guy,” Jamie said. “You could tell him a movie, and he’ll sing some random score that you wouldn’t think of.” Example: For Star Wars, he wouldn’t dare segue into something as obvious as the cantina scene or the Imperial March.

And Sydney finds a new interest seemingly each week. During the two weeks before this interview, she began hatha yoga, weaving, knitting and oil painting.

“I’m really into trying things, obviously,” she said. “I’m always searching for a new hobby.”

The siblings grew up in the Toluca Lake home of a painter mother and a music producer/songwriter father. Instruments were scattered around the house, and their father had an in-home recording studio.

“We happened to pick up the perfect instruments to be in a band, but that wasn’t intentional,” Sydney said. “We’ve (also) been in a tracking room, recording, since we were babies. When we (later) recorded our record, it was nice because we knew how it all worked. We had done it a million times.”

The Sierotas performed in front of people for the first time at a local fundraiser. Their set consisted of pop covers. From there, they expanded to the lavish rock and roll landscapes of farmers markets and cafes. Dad managed production and mom worked out logistics elements.

And so it went until 2012, when Warner Bros. took notice and signed the quartet. The following year they recorded and released Talking Dreams, a lush blend of ‘70s AM radio grooves and Britpop. The label volunteered the band – who chose the name Echosmith as a symbolic gesture to their devotion to the craft; think “blacksmith” – to join the Vans Warped Tour.

“I didn’t even really know what it was,” Sydney said. “We were a little nervous because we did know there were a lot of punk bands and bands that were different from us.”

But their uniqueness made them stand out, and they exponentially grew their fan base. A partial tour agreement was expanded to include the entirety of the tour, and Echosmith was invited to return in the summer of 2014.

By then, the Metallica T-shirt wearing punks in front of Echosmith’s stage multiplied. As did the tween and female contingent.

“A lot of those punk bands have mostly teenage girls that are going to their shows,” Sydney noted.

The first summer, the band didn’t have a single to their name, but it soon became clear that fans strongly connected with the mellow self-worth anthem “Cool Kids.” The song became their first single and was released to radio in 2014, about a year following the release of the album. It reached No. 13 on the Billboard Hot 100 chart and went platinum.

At the time of the album’s release, the band and label agreed right to hold off releasing any singles right away.

“It was one of those things where you don’t want to jump in too much,” Jamie said. “We wanted a song on the radio, but we didn’t just want to throw something on. You hear stories about labels throw(ing) singles to the radio and it doesn’t work, or blows up too fast. And then nothing happens with it. We wanted to have something underneath.”

“Cool Kids” connected with young and old alike, because many people have self-confidence weaknesses, and the song speaks to the strength that comes with self-empowerment.

Sydney and Jamie have noticed that the band has growing number of fans in their 20s, 30s, and even their parents’ ages (40s). Some assume the siblings are older than they are, Sydney said, but the band just writes what comes naturally to them.

“We’re not writing about going to the mall, but we’re also not trying to write maturely,” she said. “Naturally, we might not write songs that are typical for our age, I guess.”

The entirety of the album speaks about various types of “love.” “Cool Kids” is about loving oneself, while the other songs are about family, significant others, and even the love of adventure and daring to try something new.

“Love in all forms is something I think is overlooked,” Sydney said.

Follow editor Roman Gokhman at Twitter.com/RomiTheWriter.