Can I connect two tv antennas in parallel?
Yes you can, but unless you understand about phasing, and control the impedance  (with non-lossy things like a Wilkinson combiner or a quarter-wave transformer (don't use a lossy 6dB equal split combiner (you'll not get any more signal level))) it's unlikely to give you much benefit, and may make things worse. 

It's far better to get a longer antenna, that is a Yagi with more directors.