If someone born in 1990 were to travel to a location where time is significantly slowed down, such as near a black hole or traveling at relativistic speeds, and then return to normal time, they would indeed experience a time dilation effect compared to someone who remained in normal time.
According to the theory of relativity, time dilation occurs when an object is moving relative to another object or is in a strong gravitational field. As a result, time would pass slower for the individual born in 1990 compared to the person born in 2000 who remained in normal time.
When the person born in 1990 returns to the normal time frame, they would have experienced less time relative to the person who stayed behind. From their perspective, they would have aged less biologically compared to the person born in 2000. However, it's important to note that this effect would be relatively small unless they were subjected to extreme gravitational forces or traveled at extremely high speeds for an extended period.
It's worth mentioning that achieving time dilation effects significant enough to have a noticeable impact on aging would require reaching speeds close to the speed of light or being exposed to extremely strong gravitational fields, which are currently beyond our technological capabilities.