Why are the two constellations very similar?

No one's constellation is an isolated "sun constellation". You're talking about the sun sign.

Mercury and Venus are planets revolving around the sun, and the total solar constellation is still before or after. At the same time, it will make a person show the characteristics of adjacent constellations.

For example, I am a sun lion, but I look like a virgin, because Mercury and Venus are virgins.

Adjacent constellations are contradictory and complementary, so you have different characteristics, which is a kind of compensation. No one can be included in the characteristics of a single constellation.