Juvenile bettas typically have horizontal lines on their bodies at this stage of their development. Juvenile male bettas often have vertical stripes when they are very young. This group of siblings seems to be developing very nicely.
Both sire and dame of this spawn were singletail HM. They both carried doubletail recessively. All of the fry pictured are siblings. They do have a HM and DT cross in their genetic background from about 4 generations ago.