Herzmeh, you and Mrs. Herzmeh can arrive with 1 litre each as shown on the following UK government website. But YOU cannot be carrying 2 litres. You must each carry 1 litre.
https://www.gov.uk/duty-free-goods/a...outside-the-eu
Note the phrases, "transport them yourself" and "You can’t combine allowances with other people to bring in more than your individual allowance."
The same applies to all other types of duty free allowances. If you are bringing some gifts for example, the gifts in YOUR suitcase apply to your allowance and the gifts in Mrs. Herzmeh's suitcase apply to her allowance. You cannot combine the allowances and carry all the gifts in YOUR suitcase. This rule gets people in trouble more often than some people seem to realize.