There is Train caps that help with luggage?
 

In Liverpool street station?

What about from London St Pancras International?

Do you mean luggage porters?

yes i mean that

Short answer -- no. Railway porters are a thing of the past. Luggage is self-service only.

There are luggage carts at both St Pancras and Liverpool Street. They generally require a £1 coin to release them (you get the coin back when you return the cart).

This is not a facility generally available in the UK. If you genuinely need assistance (because you're disabled/elderly/etc., not because you've brought three anvils and four kitchen sinks) you can call up the train operating company you're using and they will try to assist.

Just for the benefit of anyone reading this who is unfamiliar with trains in the UK, the station platform beside the track is always very close to level with the train door.

As such there is no need to 'climb' / steps up into the carriages.

Indeed, most recently build or refurbished stations frequently have what is called 'step free' access (for wheel chair users) - and this meens literally roll-aboard unassisted. Even non-step free platforms are still just a single small step.

At most stations (apart from older smaller ones) there will be lift/elevator routes from the platform in addition to any involving stairs.

I do appreciate that there are some who travel with large quantites of baggage, but just post for the benefit of any who are concern about persons managing by themselves - the UK does not have the climb aboard from close to ground level seen in some other countries.

my issue is I'm having 4 big bags + 2 carry on + 2 kids in a double stroller. My wife will handle the kids, and i dunno how will i arrange. I tried to pack light but it seems impossible less than this for a month trip.

If your big bags aren't huge you could probably get them all on one luggage trolley. There are normally staff on the platforms who you can ask for help.
However travelling by tube would be awful verging on impossible - if I was you i'd take a taxi to/from the station. Presumably you won't be hauling all your luggage about for the entire trip, perhaps if you post what journeys you will have it for somebody will be able to give more detailed advice

If this all goes ahead, you will also need to consider where you're going to put all this stuff on the train. Of the train companies at the stations you mentioned, Greater Anglia, c2c, and First Capital Connect trains have next to no storage space for anything larger than a carry-on and East Midlands Trains are little better. None of these offer checked luggage (which is commonplace in the US). Eurostar is much better and has a luggage van and checking facilities. This sort of journey may lend itself better to a hire car.

Been there, done that, got the T-shirt and the hernia. (Very glad the kids are a little bit older now.) If you give us a bit more information about the journey you're actually trying to accomplish, we might be able to find better alternatives.

For instance, are you just passing through London on the way to somewhere else? Are you staying in London at all? What are your destinations/origin points for Liverpool Street and St Pancras? (I'm guessing you're coming into Liverpool Street from Stansted Airport or Harwich cruise terminal, and going on from St Pancras to Paris -- but that's just a guess)

FYI, I have had (limited) success pushing one luggage cart and pulling another -- but it's definitely a pain in the rear to do.

The Greater Anglia Norwich trains have plenty of luggage space - three luggage racks at each end of the carriage, plus storage space between back-to-back seats, plus the usual overhead racks for smaller items.

It's not just "try to assist". If you are disabled you have a right to assistance - and it's actually quite well-organised and quite well set up; you just phone a dedicated number and leave it all to them. (Not relevant to the OP's case, but I thought I'd mention it for anyone who may stumble across this thread later)

Yeah thats it. Im coming from AMS on the ferry, take the train from Harwich to london and a taxi there to my hotel for 1 week, then 1 week in paris, then train to brussels and train to ams again. I have all booked.

Ah. The morning Harwich to London train is no longer a dedicated boat train, but is a rather tatty old commuter train, which picks up many commuters on the way.

I'd recommend you seek out the tip-up seats to store luggage. These are normally at the non-London end of each 4-car unit.