Hi,
I know many here are knowledgeable in Ham radio. I often use walkie-talkies for hikes or when I go out fishing to a small lake with my son and while I'm there I hear interesting conversations on the radio. It seems like I can always get to hear the same guys, however, I cannot communicate with them. 
Is it possible to do so using a walkie-talkie?
Could I have tuned in to a frequency very close to theirs but not exactly their frequency so while I can hear them they can't hear me?

Thank you

Your walkie talkies are likely coded to communicate with each other and to ignore other coded radios.

If you lost your user manuals, you can usually find them through an online search. Read the manual.

What kind of radios are you using?

I agree it's quite possible they are getting out better than you -- whether because of antenna, power level, etc. That would mean you can HEAR but not TALK so well, with regards to them.

These are inexpensive radios. The brand is e-wor and uses 3 AAA batteries.
Very much like these ones: https://www.ebay.com/itm/174801838965

On this topic, are there some hand-helds (aka walkie-talkies) that can go 20-30 miles reliably without repeaters?  I’ve seen some advertise that range but then the reviews say otherwise.  I’d like to set up a SHTF communication network with extended family who live up to 25 miles away but don’t know much about putting together a bigger ham setup.

Unlikely, if you are using a low power FRS walkie takie. Terrain matters. They advertise 30 mile ranges, but that is untrue. Maybe... perhaps if you are on a mountain top and your family members at its base, near a nearby lake, etc. - perfectly clear line of sight.

If you can find a low-VHF high-power handheld , then perhaps, but I think such a radio would be hard to find, costs more.

You could set up a NVIS antenna in the HF band, but would require more costs and time for ham equipment.

I was looking at some GMRS ones that advertise that range ... such as this one here ...

https://www.amazon.com/gp/product/B013QIFCLE/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B013QIFCLE&linkCode=as2&tag=httpwwwchanco-20 />
It does say you need line of sight to get that range ... so somehow these don't refract around the earth's curvature like everything else always does when you try to do experiments.

On this topic, are there some hand-helds (aka walkie-talkies) that can go 20-30 miles reliably without repeaters?  I’ve seen some advertise that range but then the reviews say otherwise.  I’d like to set up a SHTF communication network with extended family who live up to 25 miles away but don’t know much about putting together a bigger ham setup.

[sigh] We've been nagging CI readers for years!

Legally unlicensed radios for FRS/GMRS bands are limited to ½ watt power.

Older Baofeng handhelds were ham radios that did not lock out the "family radio" FRS/GNRS bands and could broadcast 8 watts—a "dirty" 8 watts, but yes, 8 watts. Baofeng's newer radios have been locked out. You may find older radios on eBay that have not been locked out. Caveat emptor.

For your stated mission, I think finding those older radios is your best bet. As many have said, you'll need line-of-sight to get the range you want (or resign yourself to depending upon repeaters).

P.S. I just searched eBay and did not find any obvious candidates. Most people who have the radios you'd want, know what they have and won't sell them for the original retail price of $45-65. Sorry.

Has no one mentioned a Yagi antenna? You could hook that up and aim it in the desired direction (manually).

Interesting.  I'll look into this.  Thanks for all the input, everyone.

Has no one mentioned a Yagi antenna? You could hook that up and aim it in the desired direction (manually).

Yes the earth is flat; you only need wattage (power) to send a stronger signal. Higher frequencies (VHF, UHF) attenuate faster in the atmosphere, plus they don't propagate or negotiate around obstacles as well. So you need a stronger signal to start.

But all frequencies, low and high, propagate the same way -- in a straight line. Lower frequencies can go around obstacles easier, and it's certainly possible for them to bounce off things like water, the firmament (?) etc.

"Power" is the easy brute force solution. "Antennas" require somewhat more sophistication and tweaking. Anyone who has procrastinated on comms for years is more likely to embrace a "push to talk" solution.